Field of the Invention
Embodiments of the present invention relate generally to a multi charged particle beam writing apparatus and a multi charged particle beam writing method, and more specifically, to a method of correcting pattern position deviation and pattern dimension deviation, due to positional deviation of a beam in multi-beam writing, by modulating a dose, for example.
Description of Related Art
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits progressively narrows year by year. An electron beam writing technique intrinsically having high resolution is used for writing or “drawing” a mask pattern on a mask blank with electron beams.
As an example employing the electron beam writing technique, a writing apparatus using multi-beams can be cited. Compared with the case of writing a pattern with a single electron beam, since in multi-beam writing it is possible to irradiate multiple beams at a time, the throughput can be greatly increased. For example, in a writing apparatus employing a multi-beam system, multi-beams are formed by letting portions of an electron beam emitted from an electron gun pass through a corresponding hole of a plurality of holes in the mask, blanking control is performed for each beam, each unblocked beam is diminished by an optical system to reduce a mask image and deflected by a deflector so as to irradiate a desired position on a target object or “sample”.
In multi-beam writing, positional deviation of beams occurs due to distortion of the optical system, deviation from the design values of the aperture array for forming multi-beams, and/or the Coulomb effect, etc. There is a problem in that, if positional deviation occurs in a beam of multi-beams, positional deviation and dimension deviation also occur in a written pattern. Therefore, it is desirable to correct the positional deviation and dimension deviation of a pattern which is formed by irradiation of a beam with positional deviation. For example, it is proposed to calculate, with respect to positional deviation due to optical distortion, a shot position including the amount of the distortion, and to adjust the dose of a beam to irradiate the shot position, depending on the area density of a pattern located in the region configured on the premise of the shot position including the amount of the distortion (e.g., refer to Japanese Patent Application Laid-open (JP-A) No. 2014-007379).
However, conventionally, a method sufficiently effective for correcting positional deviation and dimension deviation of a pattern which is formed by irradiation of a beam with positional deviation has not been established yet.